Polish miners faced off against riot police as a dispute with the government over early retirement rights boiled over.
More than 5,000 miners gathered in front of the parliament building to resist a plan which will end their right to retire after 25 years on the job.
The plan, due to come into effect at the end of next year, is part of downsizing programme for the heavily endebted coal sector.
Six policemen were injured in the fighting, with one of them reportedly in a coma.
Water cannons and tear gas were used to disperse the protestors.
The miners are stepping up their pressure ahead of presidential elections due in October.
Miners have traditionally enjoyed privileged status in Poland, hailed by the Communists for their contribution to heavy industry and by the anti-Communist opposition for their role in strikes that helped overthrow the regime in 1989.